US7501145B2 - High throughput continuous pulsed laser deposition process - Google Patents

Abstract

A method includes feeding an uncoated substrate from a payout spool into a multi-chambered vacuum apparatus. The vacuum apparatus includes a plurality of deposition chambers defining an extended deposition zone, a multi-zone substrate heater located within the extended deposition zone, and multiple high-temperature superconductor (HTS) targets located within and being arranged linearly along the extended deposition zone. The multiple HTS targets include a first and second HTS target. The first and second HTS targets include a HTS material. The method farther includes translating the uncoated substrate along a translation path through the plurality of deposition chambers, impinging multiple laser beams simultaneously upon the multiple HTS targets and forming multiple overlapping plumes of HTS material within the extended deposition zone, depositing HTS material on a first major surface of the uncoated substrate to provide a coated substrate, and winding the coated substrate onto a take-up spool.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a divisional application of U.S. application Ser. No. 10/602,294 filed Jun. 23, 2003 now abandoned, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for forming a high-temperature superconducting film on a long tape substrate at speeds suitable for large-scale production, includes a spooling system for use in a high-throughput, continuous pulsed laser deposition (PLD) process.

BACKGROUND OF THE INVENTION

In the past three decades, electricity has risen from 25% to 40% of end-use energy consumption in the United States. With this rising demand for power comes an increasingly critical requirement for highly reliable, high quality power. As power demands continue to grow, older urban electric power systems in particular are being pushed to the limit of performance, requiring new solutions.

Wire forms the basic building block of the world's electric power system, including transformers, transmission and distribution systems, and motors. The discovery of revolutionary high-temperature superconductor (HTS) compounds in 1986 led to the development of a radically new type of wire for the power industry; this discovery is the most fundamental advance in wire teleology in more than a century.

HTS wire offers best-in-class performance, carrying over one hundred times more current than do conventional copper and aluminum conductors of the same physical dimension. The superior power density of HTS wire will enable a new generation of power industry technologies. It offers major size, weight, and efficiency benefits. HTS technologies will drive down costs and increase the capacity and reliability of electric power systems in a variety of ways. For example, HTS wire is capable of transmitting two to five times more power through existing rights of way.

This new cable will offer a powerful tool to improve the performance of power grids while reducing their environmental footprints. However, to date only short lengths of coated conductor wire samples have been fabricated at high performance levels with any of the conventional fabrication processes.

In order for HTS technology to become commercially viable for use in the power generation and distribution industry, it will be necessary to develop techniques for continuous, high-throughput production of HTS tape. Several challenges must be overcome in order to enable the cost-effective production of long lengths (i.e., several kilometers) of HTS-coated conductor wire.

Vapor deposition is a process for manufacturing HTS tape in which vapors of superconducting material such as YBCO are deposited on a tape-like length of buffered metal substrate, thereby forming an HTS coating on the tape substrate. Well-known vapor deposition processes include physical vapor deposition (PVD), chemical vapor deposition (CVD)), and pulsed laser deposition (PLD). PLD has shown great promise for the deposition of superconducting thin films, due in large part to its operational simplicity, its flexibility in vacuum requirements, and the congruent, stoichiometric transfer of material that results from the generation of a highly forward-directed plume from target to substrate.

In a pulsed laser deposition (PLD) process in which a laser is used to evaporate a material, where atoms of the material subsequently coat a surface that is exposed to the evaporated material, thereby forming a film on that surface. PLD is a process suitable for manufacturing HTS wires with high current-carrying capacity In this case, a target comprising a stoichiometric chemical composition of the desired layer is ablated by a pulsing laser, forming a plume of ablated material to which a buffered substrate is exposed, thereby coating the buffered substrate with the desired material and forming a coated wire or tape. Using a PLD process it is possible to deposit a superconducting layer atop a translating flexible buffered polycrystalline metal tape in a continuous, assembly line manufacturing process. However, to date only short lengths of coated conductor wire samples have been fabricated at high performance levels using prior art vapor deposition processes and equipment.

The manufacture of long lengths of HTS tapes via a PLD process necessitates a system that provides for the translation of the tapes through a deposition chamber where they receive the desired thin film coating. Youm, U.S. Pat. No. 6,147,033, dated Nov. 14, 2000, and entitled “Apparatus And Method For Forming A Film On A Tape Substrate,” provides a tape transport system particularly well suited for translating a substrate tape through a deposition chamber.

As described by Youm, the superconducting film is deposited on the tape substrate wound around a cylindrical substrate holder inserted in an auxiliary chamber housed completely within a main deposition chamber. The cylindrical substrate holder rotates during the whole deposition process. Vapors of film materials are supplied form the main chamber through an opening between the two chambers. According to Youm, it is possible to form HTS film rapidly onto a tape substrate having a length up to 300 meters. While this represents a step toward the large-scale production of HTS coated tape, it is limited in its scalability. To achieve significantly longer lengths of HTS coated tape the cylindrical substrate holder must increase in size accordingly, making it impractical to be housed within the main vapor deposition chamber. Thus, a drawback of the vapor deposition process described in Youm is that the system is not easily scalable to produce long lengths (e.g., several kilometers) of HTS coated tape and is therefore not suited for the large-scale production of HTS coated wire.

Several other challenges must be overcome in order to enable the cost-effective production of long lengths (i.e., several kilometers) of HTS coated conductor wire.

A first challenge to the continuous deposition of HTS tapes utilizing a reel-to-reel tape transport system that is not overcome by Youm is the maintenance optimum tape tension throughout the extended deposition runs necessary to high-throughput systems. If the correct level of tautness is not maintained, the tape sags. This results in a variation in the target-to-substrate distance and a compromise of the thin film uniformity.

A second technical challenge to the continuous deposition of HTS tapes utilizing a reel-to-reel tape transport system that is not overcome by Youm is the maintenance of the tape at the optimal speed throughout extended deposition runs. As the spools rotate and the tape is translated through a chamber, the tape must remain at the same position within the deposition zone, regardless of the radii of tape housed on each spool. Lateral, as well as longitudinal, movement of the tape results in an inconsistent and non-uniform deposition resulting in variations in film thickness. The importance of film uniformity cannot be an overemphasized: if there is an insufficient superconducting quality at a single point over the entire length of a few hundred meters of tape, the current carrying capacity of the entire length of tape is compromised. Further, any elements that serve to position the tape must do so in such a way as to not induce stress or strain in the tape, which may damage the delicate thin films

Another technical challenge not overcome by Youm is how to wind the tape onto a spool subsequent to its undergoing the deposition process without damaging the delicate thin film housed thereon. The ceramic grains of superconducting films may fracture if bent beyond a certain strain, which may result in a decrease in the critical current-carrying capacity of the finished superconductor tape.

To achieve the proper bonding of the evaporated material to the substrate during a typical PVD, CVD, or PLD process it is necessary to heat the substrate. Thus, a substrate heater that is capable of sustaining the substrate at a process temperature ranging typically from 500 to 1500° C. is required Current PVD, CVD, or PLD processes typically employ a stationary substrate mounted on a stationary substrate holder, where the substrate holder incorporates a heating element. Since the substrate is in direct contact with the heated substrate holder, heating of the substrate takes place by conduction.

An example of a conventional stationary substrate heater is disclosed in Chen et al., U.S. Pat. No. 6,066,836, dated May 23, 2000 and entitled “High temperature resistive heater for a process chamber”. Chen et al. describes a structure for a processing apparatus such as a chemical vapor deposition chamber that includes a resistively heated substrate holder including a support surface that includes an additional resistive heating element. The heated substrate holder is disk-shaped to accommodate a substrate, such as a wafer, in a semiconductor application. Chen's substrate heater includes a heating element that provides a single heating zone, that is, one uniform temperature is maintained across the entire substrate

However, in the case of a continuously translating substrate as is necessary for a continuous flow manufacturing process, it is difficult to maintain a uniform temperature profile using resistive heaters as disclosed by the prior art, Any local loss of contact with the heating element by a rapidly moving substrate can cause large temperature variations and in turn inhomogeneities in the coating film. Consequently, a technical challenge to overcome is how to heat a rapidly moving substrate in a continuous flow high-throughput manufacturing process for producing long lengths of HTS-coated wire.

In the case of a translating substrate in a continuous flow manufacturing process, multiple temperature zones having different temperature requirements, such as a preheating zone, a deposition zone, and a cooling zone, are desirable. Current substrate heaters do not provide multiple heating zones with differing temperature ranges as required for continuous flow manufacturing of HTS-coated wire and thus are not suited for use in the large-scale production of HTS-coated wire,

In the PLD process, a film is deposited on a substrate by the action of a laser beam impinging on a target material that is located in close proximity to the substrate, thereby creating a plume of ablated material (plasma) to which the substrate is exposed. Conventional PLD systems utilize a single laser beam that impinges on a target mounted on a target manipulator. The target manipulator provides an appropriate target rotation and oscillation. In a particular well-known example, multi-target manipulators may hold multiple targets for sequential use in a PLD process. In this case, as the material of any given target is consumed during the PLD process, the multi-target manipulator indexes from one target to the next. However, in the large-scale continuous production of HTS-coated wire, a multi-laser beam PLD process, in which multiple laser beams impinge on multiple targets simultaneously, may be used, thereby simultaneously creating multiple overlapping plumes to which a translating substrate is exposed. In this way, the deposition region is expanded in length, thereby improving the overall throughput of the PLD process compared with a single laser/single target PLD process. Conventional target manipulators are therefore of limited use in a multilaser beam PLD application.

An example of a conventional target manipulator is described in Kim et al., U.S. Pat. No. 5,942,040, entitled “Multi-Target Manipulator For Pulsed Laser Deposition Apparatus.” Kim et al. discloses a multi-target manipulator for a pulsed laser deposition apparatus, including a driving mechanism that includes a stepping motor and a motion feed for providing rotation to the target disk driving shaft and the target driving motor shaft. The driving mechanism further includes a driving transmission and head-supporting member that transmits a rotational motion for rotating the target disk and the target so as to locate a target material on the focal point of the laser beam.

Although Kim et al provides a multi-target manipulator, the multiple targets are arranged on a circular disk with the intent of being indexed from one to another for consumption one at a time. Although it is conceivable that multiple lasers could be focused on all targets simultaneously, it is not practical for a continuous flow application in which a substrate tape is translating in a straight line, thereby requiring the targets to be arranged in a straight line. A further limitation is that Kim et al.'s the multi-target manipulator provides rotation to only one target at a time. This type of multi-target manipulator is therefore not suited for use in the large-scale production of HTS-coated wire utilizing a continuously translating substrate through a deposition chamber.

It is conceivable that several target manipulators, such as Kim et al.'s multi-target manipulator, could be used in combination with multiple laser beams arranged sequentially in a straight line along the path of the translating substrate tape. However, using such an arrangement of several conventional target manipulators in a multi-laser beam PLD system is very costly and therefore not practical. Also, conventional target manipulators occupy lot of space and as a result, there will be large gaps between targets. This will result in large gaps between plumes from the targets when used with multiple lasers. Consequently, this arrangement of several conventional target manipulators is not economically or practically suited for use in the large-scale production of HTS-coated wire.

It is therefore an object of the invention to provide a tape transport system well suited to the continuous high-throughput manufacture of HTS tapes.

It is another object of the invention to provide a tape transport system that maintains optimum tape tension throughout extended deposition runs.

It is yet another object of the invention to provide a tape transport system that maintains tapes at an optimal target-to-substrate distance throughout extended deposition runs.

It is yet another object of the invention to provide a tape transport system that prevents damage to the newly deposited superconducting films as the tape winds onto a take-up spool.

It is an object of the invention to provide a substrate heater for use with a non-stationary substrate in a continuous flow vapor deposition process.

It is another object of the invention to provide a substrate heater with multiple independent heating zones for use with a non-stationary substrate in a continuous flow vapor deposition process.

It is yet another object of the invention to provide a substrate heater that achieves the desired heating of a translating substrate by a combination of conductive and radiative heating during a continuous flow vapor deposition process.

It is an object of the invention to provide a multi-target manipulator that provides multiple targets arranged in line for simultaneous use in a multi-laser beam PLD process for the large-scale production of HTS-coated wire.

It is yet another object of the invention to cost-effectively provide a multi-target manipulator for use in a multi-laser beam PLD process for the large-scale production of HTS-coated wire.

It is an object of the present invention to provide a PLD apparatus and method for forming highly uniform HTS film on a tape substrate.

BRIEF SUMMARY OF THE PRESENT INVENTION

The present invention is a PLD system and method for use in the large-scale, high-throughput production of HTS coated wire. In particular, the present invention includes a high-throughput PLD manufacturing system that provides continuous production of HTS coated tape via the deposition of, for example, yttrium-barium-copper-oxide (YBa₂Cu₃O₇or “YBCO”) film onto a buffered metal substrate.

In its simplest form, the PLD system of the present invention includes a main deposition chamber disposed between a first and second vacuum chamber. The PLD system further includes a controlled reel-to-reel spooling system capable of translating buffered metal substrate tape through the multiple chambers. The spooling system includes a payout spool disposed within the first vacuum chamber for feeding the substrate tape into the deposition chamber and a take-up spool disposed within the second vacuum chamber for receiving the HTS-coated wire. The size of the deposition chamber is unaffected by the size of the spools which is variable depending on the length of the substrate tape wound thereon.

The main deposition chamber further includes elements that allow the formation of a deposition zone that is longer than those in conventional deposition systems without sacrificing the uniformity of deposition of the coating material on the substrate. Such elements include multiple laser beams, which impinge simultaneously upon multiple targets mounted on a multi-target manipulator, thereby simultaneously forming multiple plumes of HTS particles, to which the substrate is exposed in a deposition zone.

The presence of multiple overlapping plumes arranged sequentially effectively lengthens the deposition zone wherein the substrate is exposed to the evaporant material. The thickness of the HTS film deposited onto the substrate tape is controlled by the rotational speed of a payout and take-up spool within the spooling system, thereby controlling the time that the substrate is present in the deposition zone.

The reel-to-reel tape transport system includes a pair of spools driven by a pair of identical motors that force the rotation and thereby the translation of a substrate tape at a rate of between 10 and 500 meters per hour through one or more adjacent deposition chambers in which a layer of superconducting material, such as YBCO, is deposited. The motors are managed by a controller such that, as one motor drives the spools, the other imparts an amount of resistance sufficient to provide an optimal tension in the tape. A pair of idlers maintains the tape at an optimal position as it translates through a deposition zone. The idlers come into contact with the non-coated side of the tape as the tape winds off a payout spool and onto a take-up spool; the idlers shift in their positioning so as to accommodate the changing radii of tape housed on each spool.

Subsequent to undergoing the deposition of a superconducting layer, the tape is made to wind onto a take-up spool such that the HTS-coated side winds in an orientation toward the center of the spool rather than toward the outer perimeter of the spool, as the superconducting film is less likely to be damaged when under compressive strain rather than when under tensile strain. As an additional protective measure, a length of polymer interleaf may be wound into the take-up spool between tape layers as the tape winds onto the take-up spool, thereby protecting the superconducting layer form being scratched by the non-coated side of the substrate tape.

The system also includes a scalable multi-zone substrate heater for heating by a combination of conduction and radiation a continuously translating substrate in a high-throughput continuous production vapor deposition process. The multi-zone substrate heater of the present invention is suitable for use inside a vapor deposition chamber for depositing, for example, a HTS film on a buffered metal substrate tape translating through the deposition chamber.

In order to optimally reach the desired temperature profile across the entire length of a deposition zone within the deposition chamber, the multi-zone heater embodiment of the present invention includes an arrangement of heating elements that provides multiple temperature zones. Such temperature zones include, for example, a preheating zone providing a maximum temperature of 860° C., a deposition heating zone providing a maximum temperature of 900° C., and a cooling zone providing a maximum temperature of 860° C., where the preheating zone is oriented toward the entry point of the vapor deposition zone and the cooling zone is oriented toward the exit point of the vapor deposition zone.

In another embodiment of the invention, a plurality of deposition heating zones are arranged sequentially between the preheating zone and the cooling zone in a scalable fashion to accommodate process deposition zones of varying length depending on the size of the deposition chamber and/or the desired throughput.

For use in a pulsed laser deposition (PLD) process, the multi-zone heater of the present invention includes passages that enable one or more laser beams to pass unimpeded to one or more targets, which otherwise would be obstructed by the size of such a substrate heater that is necessary to accommodate the increased deposition zone length necessary to a high throughput PLD system. The multi-zone heater also allows for accurate monitoring of the substrate temperature via thermocouples and an optical pathway disposed through its structure that enables a pyrometer to make temperature measurements to the non-coated side of the translating tape.

The system also optionally includes a multi-target manipulator apparatus. The multi-target manipulator apparatus includes a plurality of target manipulators mechanically coupled to one another in a line via a bar or platen. Each target manipulator within the multi-target manipulator apparatus includes a target holder driven by an independent drive motor that provides rotational motion to the target holder via a shaft. Furthermore, the bar or platen connecting the plurality of target manipulators one to another is mechanically coupled to a common variable-speed actuator that provides the oscillatory motion in combination with the rotational motion provided by the respective motors.

In operation, the multi-target manipulator apparatus, having multiple target holders upon which are placed multiple targets, respectively, allows multiple laser beams to impinge simultaneously upon the targets. As a result, multiple plumes of ablated material, to which a substrate is exposed for a predetermined time, are formed, thereby forming a film on the substrate. Furthermore, due to the appropriate spacing between the multiple target manipulators arranged in a line, the resulting plumes slightly overlap one to another and therefore ensure uniformity of film deposition over an expanded deposition zone length.

The multi-target manipulator apparatus of the present invention is especially suitable for use in a multi-laser beam PLD process for the large-scale production of HTS-coated wire.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a front view of the pulsed laser deposition system of the present invention, in its simplest form, for forming HTS coated tape.

FIG. 1B illustrates a front view of a typical deposition system housing a spooling system in accordance with the invention.

FIG. 2A illustrates a cross-sectional view of the pulsed laser deposition system of the present invention in operation, taken along line AA ofFIG. 1.

FIG. 2B illustrates a top view of a broad representation of a multi-laser beam PLD system to which the multi-target manipulator apparatus of the present invention is suited.

FIG. 2C illustrates a side view of the multi-laser beam PLD system.

FIGS. 2D,2E, and2F illustrate the target impingement geometries that are the result of various actions of a conventional target manipulator.

FIG. 3 illustrates a side view of a multi-zone substrate heater in its simplest form for use in a vapor deposition process for forming HTS-coated wire.

FIG. 4 illustrates an end view of the multi-zone substrate heater ofFIG. 3.

FIGS. 5A and 5B illustrate a top and side view, respectively, of a first embodiment of the multi-target manipulator apparatus of the present invention.

FIGS. 6A and 6B illustrate a top and side view, respectively, of a second embodiment of the multi-target manipulator apparatus of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A and 1B are front views of aPLD system100 of the present invention in its simplest form. ThePLD system100 includes amain deposition chamber102 arranged between afirst vacuum chamber104 and a second vacuum chamber106, where achamber wall116 having anopening117 provides separation and isolation between thedeposition chamber102 and thevacuum chamber104, and where achamber wall118 having anopening119 provides separation and isolation between the vacuum chamber106 and thedeposition chamber102. Furthermore, enclosing thedeposition chamber102, thevacuum chamber104, and the vacuum chamber106 collectively is achamber enclosure120. Theopenings117 and119 provide a passageway through which a translating substrate may travel from one chamber to the next.

Thedeposition chamber102 is a chamber designed specifically for pulsed laser deposition applications, such as a 12- or 18-inch vacuum chamber commercially available by Neocera, although those skilled in the art will appreciate that a number of alternative vendors manufacture vacuum chambers in a variety of shapes and sizes that may be implemented as thedeposition chamber102 of the present invention. The surroundingvacuum chambers104 and106 may be of a variety of dimensions and serve in the present invention to house elements of the spooling system.

Housed within thedeposition chamber102 are one or more target manipulators, for example, atarget manipulator122 that includes amotor123 and atarget holder124 mechanically connected via ashaft125. Thetarget holder124 is a mount onto which atarget136 composed of HTS material, such as YBCO or cerium oxide (CeO₂), depending upon the application, is placed. Thetarget136 is available commercially from suppliers such as Target Materials, Praxair, and Superconductive Components. In its simplest from, thetarget manipulator122 may be one of many off-the-shelf models available to the industry that enables translation and rotation (rastering) of thetarget136 and/or target indexing (target selection in multiple target holders) in such a way as to ensure a uniform wearing away of thetarget136 during the PLD process and to prevent surface irregularities or undesirable microstructures from developing on thetarget136 due to repeated ablation events in localized regions.

Alternatively, to provide maximum throughput, thetarget manipulator122 is a multi-target manipulator apparatus suitable to handle multiple instantiations of thetarget136 for use in a multi-laser PLD process. In this case, the multi-target manipulator is useful in a multiple or split laser beam PLD system having a single or multi-zone substrate heater. This multi-target manipulator suitably provides the required rotating and variable-speed side-to-side oscillating motion to multiple instantiations of thetarget136 simultaneously each having a laser beam impinging upon their surface concurrently, thereby maximizing the deposition zone and thus optimizing the throughput in the continuous production PLD process.

Multiple instantiations of thetarget holder124 of thetarget manipulator122 are oriented when installed toward asubstrate heater200 that is also housed within thedeposition chamber102. Thesubstrate heater200 is a heating device used to heat and maintain the temperature of the substrate to within a range of approximately 750 to 900° C. In its simplest form, thesubstrate heater200 may be a conductive or radiant heater that is available commercially from vendors such as Thermionics, Thermocoax, Neocera, and PVD Products. However, for the purpose of continuous, long tape deposition, a heater with combined conductive and radiative heat transfer is preferred in order to achieve optimum substrate temperature as the substrate moves through the deposition zone. Alternatively, to provide maximum throughput, thesubstrate heater200 is a multi-zone heater. Such a multi-zone heater includes multiple independently controlled and monitored temperature zones (e.g., a preheating zone providing a maximum temperature of 860° C., one or more deposition heating zones each providing a maximum temperature of 900° C., and a cooling zone providing a maximum temperature of 860° C.) arranged sequentially along the axis of the tape translation in order to optimally reach the desired temperatures across the entire length of an expanded deposition zone made possible by the use of atarget manipulator122 suitable to handle multiple instantiations of thetarget136 in combination with a multiple or split laser beam PLD system.

Furthermore, in a preferred embodiment, thesubstrate heater200 is a scalable multi-zone heater design that includes multiple “deposition heating zones” arranged sequentially along the axis of the tape translation to accommodate process deposition zones of varying length withindeposition chamber102.

The design of the multi-zone heater allows multiple laser beams to pass unobstructed to multiple instantiations of thetarget136 and allows for accurate monitoring of the substrate temperature via thermocouples throughout the continuous PLD process.

As shown in more detail inFIG. 1B, housed within thedeposition system100 is thespooling system120 in accordance with the invention. Thespooling system120 includes apayout spool128, upon which asubstrate tape140 is wound, having an associateddrive motor124 with an associatedcontroller126, all housed in thechamber104 along with anidler130. Thespooling system120 further includes a take-upspool132, onto which thesubstrate tape140 in the form of HTS-coated tape is wound, having an associateddrive motor133 with an associatedcontroller135, all housed in the chamber106 along with anidler134. Thesubstrate tape140 laces through thedeposition system100 from thepayout spool128 and then rides on the idler130 through aopening117 in thechamber wall116, and thus passes into themain deposition chamber102. Once inside thedeposition chamber102, thesubstrate tape140 subsequently passes through a deposition zone and then exits thedeposition chamber102 via anopening119 in thechamber wall118, and passes into the chamber106. The non-coated side of thesubstrate tape140 subsequently rides on the idler134 prior to being wound onto the take-upspool132. Theidlers130 and134 ensure stable positioning of the substrate tape and also ensure that the proper amount of tension is maintained on the substrate tape, thereby preventing the development of slack. The dimensions of the deposition zone are defined by atarget136, aplume146, and a substrate heater (not shown). Theplume146 is a plasma cloud resulting from the material of thetarget136 melting and subsequently evaporating explosively when impinged upon by a laser beam as is well known in a PLD process.

FIGS. 1A and 1B show the spooling system lacing though asingle deposition chamber102 as one example. However, the spooling system may span a plurality of adjacent chambers.

Thepayout spool128 is a reel onto which an extended length of thesubstrate tape140 is wound. A typical diameter of thepayout spool128 is eight inches. Thepayout spool128 may contain a protective interleaf material wound between the layers of thesubstrate tape142 contained thereon for protective purposes. The take-upspool130 is a reel onto which the substrate tape winds after it is exposed to a pulsed laser deposition process in thedeposition chamber102. A typical diameter of the take-upspool132 is eight inches. If disposed near the deposition zone, the take-upspool132 and/or thepayout spool128 may be cooled.

Themotors124 and133 are connected to thepayout spool122 and the take-upspool130, respectively. Themotors124 and133 are identical and serve one of two functions: one motor serves to drive a spool and translate thesubstrate tape140 through deposition chamber(s)102, while the other motor serves to provide a preset amount of tension in the substrate tape. InFIG. 1b, themotor133 is driving the take-upspool132 and thus translating thesubstrate tape140 through thedeposition chamber102, while themotor124 is providing a small amount of resistance to the rotation of thepayout spool128, thereby producing a desired amount of tension in translating thesubstrate tape140. Certain applications may require thesubstrate tape140 to reverse through thedeposition chamber102, e.g., in the case of in situ post deposition annealing, in which case the roles of themotor124 and themotor133 are reversed It is for this reason that themotors124 and132 are identical and capable of serving dual functions.

Thecontrollers126 and135 control the action of themotors124 and132, respectively. Thecontrollers126 and135 are responsible for maintaining the translation of thesubstrate tape140 through the deposition chamber(s)102 at the optimum speed and proper tension, as well as ensuring a compact winding of thesubstrate tape140 onto the take-upspool130. Thecontrollers126 and135 may provide real time information about the tension of thetape140 to an externally located control source or, alternately, tension may be actively monitored with the use of a tension-sensing device such as a load cell (not shown). Such a load cell mechanism may come into contact with thetape140 and communicate actively with thecontrollers126 and135 in a feedback loop. Thecontrollers126 and135 may then compare the communicated tension with a preset tension value stored within their memories and subsequently adjust the tension of thetape140 via control of themotor124 and/or133.

Theidlers130 and134 are rotating elements that are in contact with the none-coated side of thesubstrate tape140. A typical diameter of theidlers130 and134 is between three and five inches. Theidlers128 and136 maintain the translatingsubstrate tape140 at a consistent orientation within the deposition zone. Theidlers128 and136 prevent movement of thesubstrate tape142 in any direction except for that of its translation, ensuring thesubstrate tape140 is exposed to an optimum portion of theplume142. A precise distance from the plume142 (typically two inches) must be maintained to ensure a uniform and consistent deposition of material onto thesubstrate tape140. Additionally, it is likely that there may be additional pairs of idlers included in applications in which thespooling system120 translates thesubstrate tape142 through more than one adjacent deposition chambers. Theidlers128 and136 additionally allow for adjustment in the positioning of thesubstrate tape140, as is desirable when it is determined that the substrate-to-target144 distance must change.

In operation, thepayout spool122 containing thesubstrate tape140, which has been exposed to a buffer deposition process such as IBAD, is received from the buffer layer deposition processing area and is mounted in thepayout spool122 location of thespooling system120. The take-upspool130 is similarly mounted, and a leader section of tape attached to the take-upspool130 is laced under the idler136, through theslit119, in some cases through a multi-zone substrate heater, through theslit138, and under the idler128, and is spot-welded or spliced to thesubstrate tape140. The heater is turned on, themotor132 and themotor124 are engaged, thesubstrate tape140 translates through thedeposition chamber102 at a constant rate of between 10 and 500 meters per hour, and a PLD process occurs that deposits a superconducting layer atop thesubstrate tape140.

During translation of the substrate tape142 (from left to right, as seen inFIG. 1b), themotor132 drives the take-upspool130 and causes thesubstrate tape140 to translate through thedeposition chamber102. Themotor124 provides a small amount of resistance to the rotation of thepayout spool122 and thereby produces the desired amount of tension in the translating thesubstrate tape142. Thecontroller126 and thecontroller135 regulate the actions of themotor124 and themotor132, respectively, ensuring that themotors124 and133 translate thesubstrate tape142 through thedeposition chamber102 at a constant speed and optimum tension. The tension may be monitored actively by thecontrollers126 and135 or by a tension-sensing device such as a load cell that is in communication with thecontrollers126 and135. Themotor124 and themotor133 are identical and are capable of translating thesubstrate tape140 through thedeposition chamber102 in reverse, as certain applications such as post-deposition in situ annealing demand such features. Additionally, themotor124 and themotor133 may include tension-controlling devices such as clutches that control the torque imparted to the take-upspool132 and thepayout spool128. Such clutches are elements well known to the art. Theidlers128 and136 maintain the translatingsubstrate tape142 at a constant height through thedeposition chamber102, ensuring an optimum substrate deposition temperature as thesubstrate tape140 translates through or near a substrate heating element, as well as ensuring a uniform and consistent deposition of material onto thesubstrate tape140 by maintaining the optimum substrate-to-target136 distance (typically two inches). Additionally, theidlers130 and134 help to prevent any lateral motion or the formation of twists in translatingsubstrate tape140.

Thesubstrate tape140 winds onto the take-upspool132 such that the HTS-coated side of thesubstrate tape140 is oriented toward the center of the take-upspool132. The ceramic film deposited on thesubstrate tape140 is less likely to be damaged when under compressive stress than when under tensile stress, as the ceramic grains atop thesubstrate tape140 may fracture when bent beyond a certain strain, resulting in a decrease in the critical current-carrying capacity of the finished superconductor tape. As an additional protective measure, a length of polymer interleaf may be wound into the take-upspool132 between layers as thesubstrate tape140 winds onto the take-upspool132, protecting the superconducting layer of thesubstrate tape140 from being scratched by the non-coated side of thesubstrate tape140, Polymer interleaf layers may also be included in thepayout spool128 and collected by a collector spool as thesubstrate tape140 rolls off thepayout spool128. Additionally, thesubstrate tape140 may undergo silver sputtering in a chamber adjacent to thedeposition chamber102 before winding onto the take-upspool132 to provide a protective coating to thesubstrate tape140.

Thesubstrate tape140 is an extended length of buffered substrate that may have dimensions of one centimeter in width and upwards of one hundred meters in length. An example of thesubstrate140 is a buffered metal (e.g., polycrystalline nickel alloy) tape. In the case of a buffered metal tape, thesubstrate140 is composed of for example, Hastelloy, Inconel, or stainless steel that has been cleaned and polished and measures, for example, between 25 and 100 microns in thickness, with, for example, a yttria-stabilized zirconia (YSZ), cerium oxide (CeO₂) or magnesium oxide (MgO) buffer layer deposited thereon by one of several well-known deposition techniques, such as ion beam assisted deposition (IBAD). Optionally, thesubstrate140 may include “dummy tape,” or a length of non-processed substrate, at both ends to allow easier lacing through the multi-laserbeam PLD system100 and easier subsequent handling.

FIG. 2A shows a cross-sectional view of thePLD system100 in operation, taken along line AA ofFIG. 1A. As shown inFIG. 2A, it is evident that thePLD system100 of the present invention further includes alaser142 such as a Lambda Physik model STEEL 670 Excimer laser, characterized by stabilized average power of 200 watt and a pulse repetition rate up to 300 Hz. Those skilled in the art, however, will readily perceive that a variety of lasers may enable the practice of this present invention.

In operation, thelaser142 emits apulsed laser beam210 that subsequently passes through a commercially available adjustable focusoptical lens144 and then reflects off amirror146 that is a light-reflecting surface available commercially from suppliers such as Roper Scientific. ThePLD system100 includes alaser port148 that has a quartz window through which thelaser beam210 enters into thedeposition chamber102. Because a laser beam, such as thelaser beam210, is operating continuously during the PLD process, contaminate particles of the target material may tend to cloud the laser window within thelaser port148 over time. Thus, in the preferred embodiment, thelaser port148 includes a laser beam delivery system that monitors and automatically maintains alaser beam210 of constant energy by monitoring the intensity of thelaser beam210 via sensors and feeding back to a controller such that thelaser142 power level may be adjusted up or down accordingly.

Aplume212 is a plasma cloud resulting from the material of thetarget136 melting and subsequently evaporating explosively when impinged upon by thelaser beam210.

ThePLD system100 further includes various controls and monitoring devices, such as a mass flow controller (MFC)150 that regulates the mass of gas that enters thedeposition chamber102; avacuum pump152 mounted to thedeposition chamber102 via apump port154 inchamber wall120, where thevacuum pump152 may be a combination of a mechanical pump and a turbo-molecular pump and functions to assist in controlling the pressure inside thedeposition chamber102 and purging gas from thedeposition chamber102, and where thepump port154 also acts as the outlet through which gas is purged from thedeposition chamber102; apressure gauge156 that is a pressure-sensing device, such as a capacitance monometer, a hot cathode, a cold cathode, a convectron, or a number of other applicable instruments; and anelectron gun158 that during operation emits anelectron stream214 into thedeposition chamber102 and onto the deposited HTS layers of thesubstrate140 at a grazing angle less than five degrees. Theelectron stream214 impinges on the layers deposited on thesubstrate140 and is diffracted and analyzed at a RHEEDpattern analysis area160. The RHEEDpattern analysis area160 is an analysis area at which a diffraction pattern is produced due to the interaction of theincident electron stream214 and the crystalline arrangement of the surface of film deposited onto thesubstrate140. RHEED diffraction patterns, often represented by an Ewald sphere, are produced when the momentum ofincident electron stream214 and that of the diffracted electron beam differ by a reciprocal lattice vector of the deposition surface, and are used to monitor the growth, crystallinity, and crystal orientation of the film (layers deposited onto the substrate140) in situ. Additionally, other in situ monitoring tools that may be incorporated into thePLD system100 include a helium neon (HeNe) laser with a HeNe pass filter and photodiode, an X-ray diffractometer system, or an X-ray fluorescence system.

With continued reference toFIGS. 1A and 2A, the operation of thePLD system100 in its simplest form (i.e., onelaser beam210 impinging on onetarget136 forming one plume212) is as follows. Thepayout spool128, on which is wound a length ofsubstrate140 that is coated with a buffer layer as received from the buffer processing area, is mounted within thevacuum chamber104. Thesubstrate140 is laced through theopenings117 and119 in thechamber walls116 and118, respectively, and onto the take-upspool132 in vacuum chamber106, all the while being in contact with theidlers130 and134 to prevent any slack from developing in the length of thesubstrate140. Additionally, theidlers130 and134 are set such that thesubstrate140 is a predetermined distance from thetarget136. A typical distance of thesubstrate140 from thetarget136 is approximately two inches.

Thetarget136 is mounted to thetarget holder124 within the vacuum environment of thedeposition chamber102 in close proximity to thesubstrate140, onto which the evaporant material, such as YBCO, is to be deposited.

The vacuum environment of thedeposition chamber102 is developed by thevacuum pump152 and monitored by thepressure gauge156. Oxygen is pumped into thedeposition chamber102 via theMFC150. Thesubstrate140 is heated to an optimal deposition temperature between 500 and 900° C., preferably between about 750 and about 830° C., by theradiant substrate heater200. Thepulsed laser beam210, which is generated by thelaser142 located outside thedeposition chamber102, is focused by thelens144, reflects off themirror146, and is directed into thedeposition chamber102 through thelaser port148 to impinge upon a portion of thetarget136, causing the formation of theplume212, which emanates from that portion of thetarget136 radiated by thelaser beam210 toward thesubstrate140 in a highly forward-directed fashion. The particles contained in theplume212 are thus deposited onto the surface of thesubstrate140 as the tape translates through thedeposition chamber102 at a predetermined speed controlled by the rotational speed of the take-upspool132.

Thetarget136 is rastered, or rotated and translated, by thetarget manipulator122 during the laser impingement events to prevent undesirable microstructures (cones) from developing on the surface of thetarget136 and, further, to assure an even wearing away of thetarget136. As the HTS coated tape formed by the PLD process exits thedeposition chamber102 through theopening119 in thechamber wall118, it may optionally undergo silver sputtering in an adjacent chamber to provide a protective coating. Alternately, a protective film may wind onto the take-upspool132 as the superconducting tape winds onto the take-upspool132 to provide a protective barriers.

As the deposition process occurs, the in situ monitoring tools as described inFIG. 2A are used to monitor the growth, crystallinity, crystal orientation, and thickness of the film being deposited onto thesubstrate140.

Thedeposition chamber102 may additionally include several extra ports for user diagnostics or other applications, including, but not limited to, target and substrate view ports, ports for atomic absorption or emission spectroscopy, and a pair of ports for if situ ellipsometry.

To provide aPLD system100 that is highly optimized for the continuous, high throughput production of HTS wire, the translation rate of thesubstrate140 through thePLD system100 is increased by expanding the length of the deposition zone in the following manner. In an alternative embodiment that achieves all expanded length deposition zone, thePLD system100 of the present invention includes multiple instantiations of thelaser beam210 for impinging upon multiple instantiations of thetarget136 arranged sequentially along the axis of the tape translation, thereby forming multiple instantiations of theplume212 simultaneously to which thesubstrate140 is exposed. The multiple instantiations of thetarget136 are mounted onto thetarget manipulator122 that suitably designed to handle the multiple instantiations of thetarget136. The multiple instantiations of theplume212 are arranged sequentially along the axis of the tape translation and are slightly overlapping, thereby forming an expanded length deposition zone wherein thesubstrate140 is exposed to the evaporant material. Furthermore, this expanded deposition zone provides a film deposition uniformity within +/−5%. The thickness of the HTS film deposited onto thesubstrate140 is controlled by the rotational speed of the take-upspool132, thereby controlling the time that thesubstrate140 is present in the deposition zone.

Multiple instantiations of thelaser beam210 may be supplied by multiple instantiations of thelaser142, respectively, or by asingle laser142 having a laser output that is split into multiple instantiations of thelaser beam210 by optical devices that perform well-known laser splitting functions. In this case, the intensity of the laser beam from thelaser142 is sufficiently powerful, when split, to supply the energy to multiple instantiations of thelaser beam210 required for a PLD process.

With continued reference toFIGS. 1A and 2A, the operation of this alternative embodiment of the PLD system100 (i.e., multiple instantiations of thelaser beam210 impinging on multiple instantiations of thetarget136 forming multiple instantiations of theplume212 simultaneously) is as follows. Thesubstrate140 is laced through thedeposition chamber102 from thepayout spool128 to the take-upspool132 as described previously. Theidlers130 and134 are set such that thesubstrate140 is a predetermined distance from the multiple instantiations of thetarget136. A typical distance of thesubstrate140 from thetargets136 is approximately five centimeters [two inches].

Multiple instantiations of thetarget136 are mounted to multiple instalntiations of thetarget holder124, respectively, of thetarget manipulator122 within the vacuum environment of thedeposition chamber102 in close proximity to thesubstrate140, onto which the evaporant material, such as YBCO, is to be deposited. Thesubstrate140 is heated by convection to an optimal deposition temperature between 500 and 900° C., preferably between about 750 and about 830° C., by thesubstrate heater200 that in this embodiment is a radiant multi-zone substrate heater. Multiple instantiations of thepulsed laser beam210 are focused by multiple instantiations of thelens144, reflecting off multiple instantiations of themirror146, and are directed into thedeposition chamber102 through the multiple instantiations of thelaser port148. Thetarget manipulator122 suitably provides the required rotating and variable-speed side-to-side oscillating motion to multiple instantiations of thetarget136 simultaneously, each having alaser beam210 impinging upon their surface concurrently, causing the formation of multiple instantiations of theplume212, which overlap and emanate toward thesubstrate140, thereby maximizing the deposition zone and thus optimizing the throughput in the continuous production PLD process. The particles produced by multiple instantiations of theplume212 are thereby deposited onto the surface of thesubstrate140 as the tape translates through thedeposition chamber102 at a predetermined speed controlled by the rotational speed of the take-upspool132.

Several key observations can be made regarding the multiple laser beam\target\plume arrangement of thePLD system100 of the present invention:

For a given HTS film thickness, an increase in throughput is achieved that is directly proportional to the number of laser beams and targets operating simultaneously (i.e., thereby forming multiple plumes), as compared with a single laser beam system (i e., a single plume).

Alternatively, for a given substrate translation speed, an increase in HITS film thickness is achieved that is directly proportional to the number of laser beams and targets operating simultaneously (i.e., thereby forming multiple plumes), as compared with a single laser beam system (i.e., a single plume).

High throughput is achieved without sacrificing the uniformity of the deposited material.

FIG. 3 illustrates a side view of a multi-zone heater250 in accordance with the invention, in its simplest form, for use in a vapor deposition process for forming HTS-coated wire. Additionally,FIG. 4 illustrates an end view of the multi-zone heater250 ofFIG. 3.

With references toFIGS. 3 and 4, the multi-zone heater250 of the present invention includes aheater block210 that forms the main body of the multi-zone heater250. A first heating zone formed within theheater block210 is a preheatingzone212 having aradiant heating element214, such as a lamp, fed by apower feed216. Thepower feed216 is electrically connected to an external controller (not shown) for controlling the power level of theheating element214 and thereby control its temperature based on feedback to the external controller via aconventional thermocouple118 that provides temperature measurements from within the preheatingzone212. Theheating element214 within the preheatingzone212 is typically capable of providing a maximum temperature of 860° C.

A second heating zone formed within theheater block210 is adeposition zone220 having aradiant heating element222, such as a lamp, fed by apower feed124. Thepower feed124 is electrically connected to the external controller for controlling the power level of theheating element222 and thereby control its temperature based on feedback to the external controller via aconventional thermocouple226 that provides temperature measurements from within thedeposition zone220. Theheating element222 within thedeposition zone220 is typically capable of providing a maximum temperature of 900° C.

Lastly, a third heating zone formed within theheater block210 is acooling zone228 likewise having aradiant heating element230, such as a lamp, or a resistive heating element such as molybdenum disilicide or silicon carbide or nickel-iron alloys such as Kanthal, fed by apower feed232. Thepower feed232 is likewise electrically connected to the external controller for controlling the power level of theheating element230 and thereby control its temperature based on feedback to the external controller via aconventional thermocouple234 that provides temperature measurements from within thecooling zone228. Theheating element230 within thecooling zone228 is typically capable of providing a maximum temperature of 860° C.

Apartition236 provides the physical and thermal boundary between the preheatingzone212 and thedeposition zone220. Likewise, apartition238 provides the physical and thermal boundary between thedeposition zone220 and thecooling zone228. The length of the preheatingzone212, thedeposition zone220, and thecooling zone228 each measures typically between 6.25 and 7.5 cm [2.5 and 3.0 inches]. Alternatively, the length of each zone can be changed by rearranging the thermal element connection according to requirements. In operation, the maximum ΔT between the preheatingzone212 and thedeposition zone220, and between the coolingzone228 and thedeposition zone220 is typically 200° C., and the overall temperature stability of the heating zones is +/−5° C.

Ashelf240 forms the base of themulti-zone heater200. Disposed within theshelf240 is anaperture242 that is positioned within thedeposition zone220. More specifically, theaperture242 is a window that during the deposition process opens briefly to allow a plume of ablated material to reach asubstrate140 to which theaperture242 is precisely aligned as thesubstrate140 translates through thedeposition zone220. Thesubstrate140 is, for example, a buffered metal (e.g., polycrystalline nickel alloy) tape, depending upon the application.

Asusceptor244 is arranged along the entire length of themulti-zone heater200, in contact with which thesubstrate140 translates in close proximity to theheating elements214,222, and230. Thesusceptor244 provides a support for thesubstrate140 as it travels through the deposition zone. The main role of thesusceptor244 is to provide a good heat transfer to thesubstrate140 so as to maintain a uniform temperature profile in the deposition zone. Thesusceptor244 is typically as long as the heater itself and wide enough to cover the entire deposition zone The thickness of thesusceptor244 is between 5 mm and 35 mm, preferably between 10 mm and 20 mm. Thesusceptor244 is formed of a material, such as hastelloy or inconel or silicon carbide, that can conduct heat as well as transfer infrared radiation from theheating elements214,222, and230 to thesubstrate140. Thesusceptor244 must be capable of withstanding the operating temperatures of the deposition process. To enable good thermal conduction, the susceptor is manufactured with a large radius of approximately 5 to 10 m. This radius enables the tape to be taut against the susceptor. The susceptor is thermally stable so that it does not deform when exposed to the high temperatures. Any deformation will prevent good contact between the substrate and the susceptor. Lastly, thesusceptor244 prevents the plume from contacting the inner components of themulti-zone heater200.

Acoolant chamber246 formed within theheater block210 provides containment for a coolant, such as water, to flow within theheater block210. The coolant is necessary to prevent thermal diffusion from themulti-zone heater200 to other elements within the deposition chamber. The coolant enters thecoolant chamber246 via a plurality of coolant inlets248 and exits via a plurality of coolant outlets250.

Themulti-zone heater200 is suitable to operate inside a deposition chamber, such as a PLD chamber, and thus is secured within the chamber via a plurality of standoffs252. Lastly, and with reference toFIG. 4, several free space paths within themulti-zone heater200 are provided to either thetarget136 or thesubstrate140. More specifically, achannel254 provides a free space optical path for an external pulsed laser beam directed at thetarget136 during the deposition process. The required incident angle of the laser onto thetarget136 is typically 45 degrees. Multiple slots256, forexample slots256aand256b, provide a free space path to the deposition side of thesubstrate140, thereby allowing Fourier Transform Infrared (FTIR) spectroscopy analyses of thesubstrate140 during the deposition process. FTIR measurements yield information about both the temperature of thesubstrate140 and the thickness and uniformity of the film being deposited on thesubstrate140. Achannel258 is a free space path for the sensing mechanism of a pyrometer (not shown), a non-contact temperature-sensing device for monitoring the temperature of the non-deposition side of thesubstrate140.

With continued reference toFIGS. 3 and 4, the operation of themulti-zone beater200 in its simplest form is as follows. Themulti-zone heater200 is mounted within a deposition chamber, such as a PLD chamber, in such a way that the preheatingzone212 is oriented toward the entry point of the vapor deposition chamber and, conversely, thecooling zone228 is oriented toward the exit point of the vapor deposition chamber. Thesubstrate140 is fed into the deposition chamber, passing through theheater block210 of themulti-zone heater200 of the present invention via the cavity formed by theshield244.

The temperature of the preheatingzone212 is set typically to between 750 and 830° C. via theelement214 under the control of the external controller connecting to thepower feed216. The temperature of thedeposition zone220 is set typically to about 850° C. via theelement222 under the control of the external controller connecting to thepower feed124. Lastly, the temperature of thecooling zone228 is set typically to between 750 and 830° C. via theelement230 under the control of the external controller connecting to thepower feed232.

Thermocouples218,226, and234 are placed in holes drilled in the body of thesusceptor244 itself and provide continuous temperature measurement feedback to the external controller such that the power level of theelements214,222, and230, respectively, may be adjusted upon the detection of any temperature fluctuations during the deposition process, thereby maintaining the desired temperature within each zone. By placing the thermocouples in body of the susceptor, a better temperature stability can be maintained.

Thesubstrate140 translates along the length of themulti-zone heater200 in a flow direction from the preheatingzone212 to thedeposition zone220 and finally exiting through thecooling zone228. The tension and translation speed of thesubstrate140 are maintained in a controlled fashion to achieve proper film uniformity and thickness.

The preheatingzone212 raises the temperature of thesubstrate140 to between 750 and 830° C., preparing it for thedeposition zone220. Once inside thedeposition zone220, the temperature of thesubstrate140 rises further to about 850° C. and a film of HTS material is deposited onto thesubstrate140 via exposure to a plume of PITS material.

The plume of HTS material is generated by a pulsed laser beam impinging on the surface of theHTS target136 viachannel254 where the plume of PITS material enters themulti-zone heater200 via theaperture242 that is synchronized with the pulsed laser beam impinging on thetarget136. Having passed through thedeposition zone220, the translatingsubstrate140 passes into thecooling zone228 where the temperature is lowered to between 750 and 830° C., preparing thesubstrate140 to exit the deposition chamber.

Slots256aand256bprovide unobstructed paths to the deposition surface of thesubstrate140 to accommodate FTIR spectroscopy analyses throughout the deposition process. The FTIR spectroscopy yields information about the temperature, the thickness, and the uniformity of the film being deposited on thesubstrate140. Likewise, thechannel258 provides an unobstructed path to the non-deposition surface of thesubstrate140 so that the pyrometer (not shown) may monitor the temperature of the non-deposition surface of thesubstrate140. Lastly, coolant continuously circulates through thecoolant chamber246 via the coolant inlets248 and the coolant outlets250 and thereby maintains the temperature of theheater block210 and associated hardware at an acceptable level to prevent damage due to excessive heating.

Alternatively, it is noted that themulti-zone heater200 of the present invention is not limited to asingle preheating zone212,deposition zone220, andcooling zone228, as shown inFIG. 1. Themulti-zone heater200 of the present invention is scalable to any number of preheatingzones212,deposition zones220, and coolingzones228. For example, to support a high-throughput manufacturing process for the continuous flow production of HTS-coated wire, an expanded deposition region is beneficial. Such an expanded deposition region is, for example, between about 25 and 65 cm [10 and 25 inches], preferably between about 30 and 37.5 cm [12.5 and 15.0 inches] in length. In this embodiment, themulti-zone heater200 is a scalable multi-zone heater design that includesmultiple deposition zones220 arranged sequentially to accommodate process deposition regions of varying length within a deposition chamber, where the deposition chamber hasmultiple targets136 with multiple laser beams impinging simultaneously on their respective surfaces, thereby exposing thesubstrate140 to multiple overlapping plumes of HTS material simultaneously along the length of this expanded deposition region viamultiple apertures242.

FIGS. 2B and 2C illustrate a top view and side view, respectively, of an embodiment of the present invention utilizing a multi-laser beam PLD system in conjunction with the multi-target manipulator apparatus of the present invention. Amulti-laser PLD system300 broadly represents the operation of a multi-laser beam PLD system. AlthoughFIGS. 2B and 2C illustrate a multi-laser PLD application, the system is also suited for use with a split laser beam PLD system.

FIGS. 2B and 2C illustrate themulti-laser PLD system300, which includes a plurality of lasers142 (e.g., alaser142a, alaser142b, and alaser142c) producing a plurality of laser beams210 (e.g., alaser beam210a, alaser beam210b, and alaser beam210c), respectively, that pass through a chamber wall316 via windows and strike a plurality of targets136 (e.g., atarget136a, atarget136b, and atarget136c), respectively, at an angle within a PLD chamber. Thelasers142 are, for example, Lambda Physik model LPX 308i lasers, characterized by a medium to high duty cycle with a pulse repetition rate up to 100 Hz. Alternative examples of thelasers142 are Lambda Physik model STEEL 670 or STEEL 1000 Excimer lasers, capable of pulse repetition rates up to 350 Hz.

In the case of a PLD system for continuous production of HTS-coated tape, thetargets136 are composed of HITS material, such as yttrium-barium-copper-oxide (YBa₂Cu₃O₇or “YBCO”) or cerium oxide (CeO₂), depending upon the application. Thetargets136 are available commercially from suppliers such as Target Materials, Praxair, and Superconductive Components.

In operation, thelasers142a,142b, and142cproducing thelaser beams210a,210b, and210c, respectively, that pass though their respective windows in the chamber wall316 and strike thetargets136a,136b, and136c, respectively, as illustrated inFIG. 2B. As a result, multiple plumes212 (e.g., aplume212a, aplume212b, and aplume212c) of ablated material (plasma) are formed simultaneously, as illustrated inFIG. 2C. In the example ofFIGS. 2B and 2C, theplumes212a,212b, and212care deposited simultaneously on asubstrate140 due to the simultaneous action oflaser beams210a,210b, and210cimpinging on thetargets136a,136b, and136c, respectively, which are located in close proximity to thesubstrate140, typically about five centimeters [two inches].

Thetargets136a,136b, and136care spaced in such a way as to obtain the desired plume overlap, and hence provide a uniform deposition over an expanded length of thesubstrate140.

FIGS. 2D,2E, and2F illustrate the target impingement geometries that are the result of various actions of a conventional target manipulator.FIGS. 2D,2E, and2F are provided as background and to gain a basic understanding of the operation of any state of the art target manipulator including a first embodiment of the multi-target manipulator apparatus of the present invention that is shown inFIGS. 5A and 5B, and a second embodiment of the multi-target manipulator apparatus of the present invention that is shown inFIGS. 6A, and6B.

As well known in the art, target manipulators provide rotational motion as well as side-to-side oscillation. The side-to-side oscillation is provided with variable speed to optimize the target material usage. For illustration only,FIGS. 2D,2E, and2F incrementally demonstrate each motion and the resulting target usage.

With reference to the top and cross-sectional views ofFIG. 2D,FIG. 2D illustrates thetarget136 having rotational motion only and a resulting continuouscircular trench312ahaving sloped walls. Thetrench312ais formed in thetarget136 by the action of the laser beam striking the surface of thetarget136. As thetarget136 rotates, the sloped walls of thetrench312aat a laser impingement area308acauses the direction of theplume212 to be tilted toward theincoming laser beam210 instead of remaining perpendicular to the surface of thetarget136 and properly directed toward thesubstrate140. The result is that the deposition process is not uniform or efficient. Additionally, the center area of thetarget136 remains unused, therefore limiting the time of operation. Consequently, a simplerotating target136, alone, is not acceptable.

With reference to the top and cross-sectional views ofFIG. 2E,FIG. 2E illustrates thetarget136 having rotational motion and uniform-speed side-to-side oscillation and a resulting much larger circular laser impingement area308bhaving sloped walls. Atrench312bis formed in thetarget136 by the action of the laser beam striking the surface of thetarget136. The dish-shapedtrench312bis formed in thetarget136, where the depth of the dish-shapedtrench312bis not uniform across the full diameter of the dish-shapedtrench312b. Again, the sloped walls of thetrench312bat the laser impingement area308bcauses the direction of theplume212 to be tilted toward the incoming laser beam instead of remaining perpendicular to the surface of thetarget136 and properly directed toward thesubstrate140. Although the time of operation is increased because a larger target area is being utilized, the rotating and uniform-speed side-to-side oscillating motion of thetarget136 is still not acceptable.

With reference to the top and cross-sectional views ofFIG. 2F,FIG. 2F illustrates thetarget136 having rotational motion and variable speed side-to-side oscillation and a large circular laser impingement area308chaving perpendicular walls. Atrench312cis formed in thetarget136 by the action of the laser beam striking the surface of thetarget136. The dish-shapedtrench312cis formed in thetarget136, where the depth of the dish-shapedtrench312cis uniform across the full diameter of the dish-shapedtrench312cdue to the variable side-to-side speed control (i.e., the side-to-side motion is at its highest speed when the laser beam translates across the center area of thetarget136 and is at its lowest speed when the laser beam translates near the outer radius of the target136). Consequently, the perpendicular walls of thetrench312cat the laser impingement area308ccauses the direction of theplume212 to remain perpendicular to the surface of thetarget136 and properly directed toward thesubstrate140. Nearly all of thetarget136 material is consumed, as compared with the simplerotating target136, or the rotating and oscillating withuniform speed target136. As a result, the combination of the rotating and variable speed side-to-side oscillating motion of thetarget136 provides maximum operation time by allowing the maximum amount oftarget136 material to be used before replacement it needed. The rotating and variable-speed side-to-side oscillating motion of thetarget136 is acceptable.

FIGS. 5A-5B and6A-6B illustrate additional embodiments, respectively, of a multi-target manipulator in accordance with the invention that provides the rotational motion and variable speed side-to-side oscillation as described inFIG. 2F for multiple targets simultaneously in a PLD application.

In a first embodiment,FIGS. 5A and 5B illustrate a top and side view, respectively, of amulti-manipulator assembly350 of the present invention. Themulti-manipulator assembly350 includes arotator assembly310a, arotator assembly310b, and arotator assembly310c. Therotator assembly310afurther includes amotor306amechanically connected to atarget holder124avia ashaft316a. Therotator assembly310bfurther includes amotor306bmechanically connected to atarget holder124bvia ashaft316b. Likewise, therotator assembly310cfurther includes amotor306cmechanically connected to atarget holder124cvia ashaft316c. Therotator assemblies310a,310b, and310care mechanically interconnected by feeding theshafts316a,316b, and316c, respectively, through asupport bar318. Theshafts316a,316b, and316cmay be solid shafts that pass through thesupport bar318 and allowed to rotate via conventional bearing assemblies inserted within thesupport bar318. Alternatively, theshafts316a,316b, and316cmay be an assembly where each includes a hollow cylinder connecting the outer housings of themotors306a,306b, and306c, respectively, to thesupport bar318, and where within each hollow cylinder is a rotating shaft passing entirely though thesupport bar318 and coupling to thetarget holders124a,124b, and124c.

Themulti-manipulator assembly350 further includes aconnection rod320aand aconnection rod320bmechanically connected to thesupport bar318 at opposing ends. The position and orientation of theconnection rods320aand320bis not limited to that shown inFIG. 5B. Alternative positions and orientations are possible. A variable-speed side-to-side actuator (not shown) is mechanically attached to theconnection rods320aand320b. Therotator assemblies310a,310b, and310care suspended from thesupport bar318 within the multi-laser PLD system, and are free to move with the action of the variable-speed side-to-side actuator. Furthermore, to provide mechanical stability, themotors306a,306b, and306care mechanically coupled to one another and to thesupport bar318 via abracket322.

Alternatively, a single motor may be mechanically connected using conventional methods to all of the threeshafts316a,316b, and316c, subsequently driving thetarget holders124a,124b, and124c, respectively.

The diameter “d” of thetarget holders124a,124b, and124cis typically less than two inches so as to enable optimum inter-target spacing and, thus, optimum plume overlap and deposition uniformity. The spacing “e” between the center points of thetarget holders124a,124b, and124cis set to allow for the optimum plume overlap. The length “l” of thesupport bar318 may vary depending on the application and specific mounting requirements. The width “w” and thickness “t” of thesupport bar318 are dimensions suitable to accommodate theshafts316a,316b, and316cand are also dimensions suitable to provide strength to thesupport bar318 to handle the overall mass of themulti-manipulator assembly350.

If themulti-manipulator assembly350 is located entirely within the deposition chamber of the multi-laser PLD system when installed, the variable-speed side-to-side actuator (not shown) and themotors306a,306b, and306care vacuum-compatible. Alternatively, if the variable-speed side-to-side actuator and themotors306a,306b, and306care located outside of the deposition chamber of themulti-laser PLD system100 when installed, thesupport bar318 and theshafts316a,316b, and316care fed through the chamber wall316 such that a vacuum seal is maintained and such that the side-to-side motion of themulti-manipulator assembly350 is still allowed.

In operation, thetargets136a,136b, and136care glued onto thetarget holders124a,124b, and124c, respectively, using a silver paste, such as Ted Pella. Therotator assemblies310a,310b, and310care activated simultaneously to provide simple rotating motion to thetarget holders124a,124b, and124c, respectively, and subsequently to thetargets136a,136b, and136c, respectively, via the action of theconventional motors306a,306b, and306c, respectively. The variable-speed actuator (not shown) attached to theconnection rods320aand320bis activated to provide the variable-speed side-to-side oscillating motion to thetarget holders124a,124b, and124c.

As a result, themulti-manipulator assembly350 of the present invention provides the rotating and variable-speed side-to-side oscillating motion to thetargets136a,136b, and136c, thereby providing optimized operation time required in a high-throughput PLD process. Additionally, the use of themulti-manipulator assembly350 of the present invention in a PLD process allows a faster film deposition process for a given thickness or allows for a thicker film deposition for a given PLD process speed.

It is important to note that themulti-manipulator assembly350 of the present invention is not limited to three rotator assemblies as shown inFIGS. 5A and 5B. Themulti-manipulator assembly350 of the present invention could be implemented with any number of rotator assemblies.

In a second embodiment,FIGS. 6A and 6B illustrate a top and side view, respectively, of amulti-manipulator assembly400 of the present invention. Themulti-manipulator assembly400 is identical to themulti-manipulator assembly350 ofFIGS. 5A and 5B, differing only in that therotator assemblies310a,310b, and310care mounted on asupport plate410 instead of interconnecting with thesupport bar318. As inFIGS. 5A and 5B, a plurality of theconnection rods320a,320b,320c, and320dare mechanically connected to thesupport plate410 at each corner. The position and orientation of theconnection rods320a,320b,320c, and320dis not limited to that shown inFIGS. 6A and 6B. Alternative positions and orientations are possible. As inFIGS. 5A and 5B, a variable-speed actuator (not shown) is mechanically attached to theconnection rods320a,320b,320c, and320d.

The operation is identical to that of themulti-manipulator assembly350 described inFIGS. 5A and 5B, differing only in that the entire assembly, including therotator assemblies310a,310b, and310c, are subjected to the variable-speed side-to-side oscillating motion of the actuator.

If themotors306a,306b, and306care vacuum-compatible motors, themulti-manipulator assembly400 is located entirely within the multi-laser PLD system. Alternatively, themotors306a,306b, and306cmounted on thesupport plate410 are disposed outside of themulti-laser PLD system100 and theshafts316a,316b, and316care fed through the chamber wall.

Claims (19)

1. A method comprising:

feeding an uncoated substrate from a payout spool into a multi-chambered vacuum apparatus, the vacuum apparatus comprising plurality of deposition chambers defining an extended deposition zone, a multi-zone substrate heater located within the extended deposition zone, multiple high-temperature superconductor (HTS) targets located within and being arranged linearly along the extended deposition zone, the multiple HTS targets including a first HTS target and a second HTS target, the first HTS target comprising a HTS material and the second HTS target comprising said HTS material;

translating the uncoated substrate along a translation path through the plurality of deposition chambers;

impinging multiple laser beams simultaneously upon the multiple HTS targets and forming multiple overlapping plumes of HTS material within the extended deposition zone while imparting rotary and oscillatory motion to the multiple targets, wherein the multiple HTS targets oscillate in a direction parallel to the translation path;

depositing HTS material on a first major surface of the uncoated substrate from the multiple overlapping plumes to provide a coated substrate; and

winding the coated substrate onto a take-up spool.

2. The method ofclaim 1, wherein the multi-zone substrate heater comprises at least three zones.

3. The method ofclaim 1, wherein the multi-zone substrate heater heats the uncoated substrate by at least one of conductive and radiative heat transfer.

4. The method ofclaim 1, wherein the multi-zoned substrate heater comprises a susceptor.

5. The method ofclaim 4, wherein the uncoated substrate further comprises a second major surface, the second major surface opposing and being co-planer to the first major surface and the second major surface facing the susceptor.

6. The method ofclaim 5, wherein the second major surface of the uncoated substrate is in contact with the susceptor.

7. The method ofclaim 4, wherein the uncoated substrate is maintained in contact with the susceptor as it translates through the deposition zone.

8. The method ofclaim 7, wherein the susceptor has a transversely concavely curved outer surface along which the uncoated substrate translates.

9. The method ofclaim 8, wherein the susceptor has a radius of curvature of about 5 to about 10 meters.

10. The method ofclaim 1, wherein the uncoated substrate is heated to a deposition temperature between about 500° C. and about 900° C.

11. The method ofclaim 10, wherein the uncoated substrate is heated to a deposition temperature between about 750° C. and about 830° C.

12. The method ofclaim 1, wherein the uncoated substrate is translated at a speed of 10 to 500 meters per hour.

13. The method ofclaim 1, wherein the uncoated substrate comprises a nickel based alloy.

14. The method ofclaim 1, wherein the multiple targets are coupled to a common target manipulator, such that the targets undergo identical oscillatory motion.

15. The method ofclaim 1, wherein the HTS material comprises REBa₂Cu₃O_7-x, wherein RE is a rare earth element.

16. The method ofclaim 15, wherein the HTS material comprises YBa₂Cu₃O₇.

17. The method ofclaim 1, wherein the multiple laser beams are produced by different lasers.

18. The method ofclaim 1, wherein winding the coated substrate onto the take-up spool includes winding a length of polymer interleaf between layers of the coated substrate tape.

19. The method ofclaim 1, wherein the uncoated substrate has a length to width ratio of not less than about l0³.

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